What is the SI unit of electric potential difference?
A Ampere
B Ohm
C Volt
D Watt
Electric potential difference is measured in volts (V), representing the work done to move a unit charge between two points in an electric field.
Which of the following factors affects the inductance of a coil?
A Number of turns
B Length of the coil
C Material of the core
D All of the above
The inductance of a coil depends on the number of turns, the length of the coil, and the permeability of the core material.
What happens to the impedance of an AC circuit with an inductor as the frequency increases?
A Impedance increases
B Impedance decreases
C Impedance remains constant
D Impedance becomes zero
Inductive reactance (XL = 2πfL) increases with frequency, causing the total impedance to increase.
Which electrical quantity is measured by a galvanometer?
A Voltage
B Current
C Power
D Resistance
A galvanometer is a sensitive device used to measure small currents in a circuit.
What type of current is produced by a battery?
A Alternating Current (AC)
B Direct Current (DC)
C Pulsating Current
D Static Current
Batteries produce direct current (DC), where the flow of electric charge is unidirectional.
What is the role of a commutator in a DC machine?
A To generate current
B To convert AC to DC
C To ensure unidirectional current
D To step up voltage
The commutator reverses the current direction in the armature winding of a DC machine, maintaining unidirectional current flow.
Which device is used to measure alternating current (AC) and direct current (DC)?
A Multimeter
B Galvanometer
C Wattmeter
D Oscilloscope
A multimeter is a versatile instrument that can measure AC, DC, voltage, resistance, and sometimes other parameters.
What happens to the resistance of a conductor if its length is doubled?
A Resistance doubles
B Resistance is halved
C Resistance remains the same
D Resistance becomes zero
Resistance (R) is directly proportional to the length (L) of a conductor: R = ρL / A. Doubling L doubles R.
What is the primary function of a choke in a tube light circuit?
A To step up voltage
B To limit current
C To convert AC to DC
D To increase resistance
A choke is an inductor that limits the current in a tube light circuit, ensuring safe and efficient operation.
Which of the following is an application of Ohm’s Law?
A To calculate resistance in a circuit
B To determine the power consumed by a device
C To measure energy
D To step up voltage
Ohm’s Law (V = IR) is used to calculate resistance when voltage and current are known.
What is the primary material used for electrical wiring?
A Aluminum
B Copper
C Steel
D Iron
Copper is widely used in electrical wiring due to its excellent conductivity, ductility, and resistance to corrosion.
What is the purpose of an electrical diagram?
A To measure current
B To visualize the connection of components
C To regulate voltage
D To reduce power loss
Electrical diagrams illustrate the connections and layout of components in a circuit for easy understanding and troubleshooting.
Which safety device is designed to trip when a ground fault occurs?
A Circuit breaker
B Residual Current Device (RCD)
C Fuse
D Transformer
An RCD trips the circuit when it detects leakage current to ground, preventing electric shocks.
Which law governs the relationship between magnetic flux and induced EMF?
A Ohm’s Law
B Faraday’s Law
C Kirchhoff’s Law
D Coulomb’s Law
Faraday’s Law states that the induced EMF in a circuit is proportional to the rate of change of magnetic flux through it.
What happens to the total resistance in a parallel circuit as more resistors are added?
A It increases
B It decreases
C It remains constant
D It becomes zero
Adding resistors in parallel reduces the total resistance, as \( 1/R_{\text{total}} = 1/R_1 + 1/R_2 + \dots \).
What type of current flows in both directions periodically?
A Alternating Current (AC)
B Direct Current (DC)
C Pulsating Current
D Static Current
Alternating current (AC) reverses its direction periodically, following a sinusoidal waveform.
What is the purpose of using a step-down transformer?
A To increase voltage
B To decrease voltage
C To store energy
D To regulate current
A step-down transformer reduces the voltage to a safer or more usable level while increasing current proportionally.
Which device protects electrical appliances from voltage spikes?
A Circuit breaker
B Surge protector
C Fuse
D Resistor
A surge protector shields electrical appliances from voltage spikes by redirecting excess voltage safely to the ground.
What is the unit of electrical power?
A Volt
B Ampere
C Joule
D Watt
Electrical power is measured in watts (W), representing the rate at which electrical energy is consumed or produced.
Which device is used to measure high voltages?
A Multimeter
B Voltmeter
C Megger
D Potential Transformer
A potential transformer is used to measure high voltages by stepping down the voltage to a safe level for measurement instruments.